qualitative  quantitative
methods
analysis
empirical  molecular
CH2
C2H4; C5H10
molecular  structural
C2H6O
CH3CH2OH
CH3-O-CH3
formula
formula
alcohol
ether
One of the most fundamental theories is the structural theory. Two
central premises are fundamental:
1. The atoms of the elements in organic compounds can form a fixed
number of bonds. The measure of this ability is called valence.
Carbon is tetravalent; that is, carbon atom form four bonds.
Oxygen is divalent; oxygen atoms form two bonds. Hydrogen (and
usually) the halogens are monovalent; their atoms form only one
bond.
2. A carbon atom can use one or more of its valences to form bonds to
other carbon atoms.
carbon-carbon bonds
single bond
double bond
triple bond
Two major types of chemical bonds:
[1] The ionic (or electrovalent) bond, formed by the transfer of one or
more electrons from one atom to another to create ions.
[2] The covalent bond, a bond that results when atoms share
electrons.
1
Carbon’s ability to form strong covalent bonds to other carbon atoms
is the single property of the carbon atom that – more than any other –
accounts for the very existence of a field of study called organic
chemistry. It is this property too that accounts in part for carbon being
the element around which most of the molecules of living organisms
are constructed. Carbon’s ability to form as many as four strong bonds
to other carbon atoms and to form strong bonds to hydrogen, oxygen,
sulphur, and nitrogen atoms as well. provides the necessary versatility
of structure that makes possible the vast number of different
molecules required for complex living organisms.
HYDROCARBONS
homologous series:
alkanes

hydrocarbons whose molecules have
a carbon - carbon single bond
paraffins
saturated compounds
ALKANE
methane
ethane
propane
n-butane
pentane
hexane
heptane
octane
nonane
decane
undecane
etc.
ALKYL GROUP
methyl
ethyl
propyl
isopropyl
n-butyl
pentyl
hexyl
ABBREVIATION
MeEtPri-Prn-BuPeHe-
General formula for alkanes is R-H (CnH2n+2).
R-  CnH2n+1 -
2
alkenes

hydrocarbons whose molecules have
a carbon - carbon double bond
olefins
unsaturated compounds
ethene (IUPAC name)
propene
alkynes

cycloalkanes

ethylene (common name)
propylene
hydrocarbons whose molecules have
a carbon - carbon triple bond
ethyne (IUPAC name)
acetylene (common name)
propyne
methylacetylene
cycloalkenes

cyclopropane
cyclobutane
cyclohexane
decaline
decahydronaphthalene
cyclopentene
cyclohexene
tetraline
tetrahydronaphthalene
arene aromatics
benzene (IUPAC)
methylbenzene
dimethylbenzenes
3
benzene (common)
toluene
xylenes (o-, m-, and p-)
isomerisation
structural; normal n- and iso-compounds i-compound
n-hexane; iso-hexane or i-hexane
cis-trans;
cis-trans isomerization is not possible if one carbon atom of the
double bond bears two identical groups (atoms)
Which of the following alkenes can exist as cis-trans isomers? Write
their structures.
a. CH2=CHCH2CH3
b. CH3CH=CHCH3
c. CH2=C(CH3)2
d. CH3CH2CH=CHCl
Alcohols and ethers may be considered as organic derivatives of
water.
ethyl alcohol
ethyl + hydroxyl groups
ethanol (IUPAC)
ethyl alcohol (common)
ether
the functional group of an ether



COC
 

CH3OCH3 methoxymethane (IUPAC)
dimethyl ether (common)
Amines may be considered as organic derivatives of ammonia.
Aldehydes and ketones
the carbonyl group
4
ethanal (IUPAC)
formaldehyde
acetaldehyde (common)
propanone (IUPAC)
acetone (common)
Carboxylic acids; the functional group of them is the carboxyl group
(carbonyl + hydroxyl).
methanoic acid
ethanoic acid
propanoic acid
butanoic acid
pentanoic acid
formic acid
acetic acid
propionic acid
butyric acid
valeric acid
hexadecanoic acid
octadecanoic acid
fatty acids:
palmitic acid
stearic acid
Esters
methyl ethanoate
methyl acetate
Haloalkane
chloroethane
ethyl chloride
Amine
methanamine
methylamine
5
PHYSICAL PROPERTIES OF ALKANES AND CYCLOALKANES
If we examine the unbranched alkanes in Table 4.4 we notice that each alkane
differs from the preceding one by one CH2 group. Butane, for example, is
CH3(CH2)2CH3 and pentane is CH3(CH2)3CH3. A series of compounds like this,
where each member differs from the next member by a constant unit, is called a
homologous series. Members of a homologous series a5e called homologs.
At room temperature (25oC) and 1-atm pressure the first four members of the
homologous series of unbranched alkanes are gases; the C5-C17 unbranched
alkanes (pentane to heptadecane) are liquids; and the unbranched alkanes with
18 and more carbon atoms are solids.
Boiling points. The boiling points of the unbranched alkanes show a regular
increase with increasing molecular weight. Branching of the alkane chain,
however, lowers the boiling point. As examples consider the C6h14 isomers.
Hexane boils at 68oC, and 2-methylpentane and 3-methylpentane, each having
one branch, boil lower at 60.3 and 63.3oC, respectively. 2,3-Dimethylbutane and
22-dimethylbutane, each with two branches, boil lower still at 58 and 49.7 oC,
respectively.
Part of the explanation for these effects lies in the van der Waals forces. With
unbranched alkanes, as molecular weight increases, so too does molecular size,
and even more importantly molecular surface areas. With increasing surface
area, the van der Waals forces between molecules increase, therefore, more
energy (a higher temperature) is required to separate molecules from one
another and produce boiling. Chain branching, on the other hand, makes a
molecule more compact, reducing its surface area, and with it the strength of the
van der Waals forces operating between it and adjacent molecules; this has the
effect of lowering the boiling point.
6